Water-based paint composition

ABSTRACT

A water-based paint composition has the ability to decompose ozone and includes a manganese oxide-based catalyst, an activated carbon, a polyacrylate-based dispersant, a water-soluble resin, a pH adjuster, and a water-based solvent.

IN CORPORATION BY REFERENCE

The present invention is based on Japanese Patent Application No.2019-55020, filed on Mar. 22, 2019, the contents of which are herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a water-based painting composition,which is applied to, for example, car body surfaces exposed to air flowin traveling. The water-based painting composition allows ozonedecomposition. In particular, the present invention relates to awater-based painting composition having good storage stability and highperformance to decompose ozone.

BACKGROUND ART

Volatile organic compounds (VOC) such as nitrogen oxides (NOx) andhydorocarbons (HC), which are included in car exhaust or factory fumes,change to photochemical oxidants (O_(x)) through chemical reaction withoxygen in air or photochemical reaction with ultra violet in sunlight.Such photochemical oxidants, which are air pollutants or environmentalload substances, mainly include ozone (O₃) and cause photochemical smog.In Japan, photochemical oxidants of 0.06 ppm and low per unit time isrequired as environmental standard. However, currently, theconcentration of photochemical oxidants is above environmental standard.While, environmental awareness rises. It is therefore desired to reducephotochemical oxidants rapidly.

Thus, ozone decomposition has been proposed to prevent photochemicalsmog while the emission of volatile organic compounds including nitrogenoxides has been regulated.

In some areas, for example, California in U.S.A., an air purificationsystem has been examined. The air purification system employs vehicleswith radiators carrying an ozone destruction catalyst. cars using adirect ozone reduction (DOR) technology, specifically, cars having anair purification device, which allow ozone in air to be decomposed byozone destruction catalyst, has been put into practical use. InCalifornia in U.S.A., the cars using a direct ozone reduction (DOR)technology and their manufacturer can receive predetermined privileges(NMOG credit certification) as they serve to reduction of exhaust ofnon-methane organic gases (NMOG), which causes photochemical smog.

With regard to a radiator carrying ozone destruction catalyst, JapaneseUnexamined Patent Application Publication (Translation of PCTApplication) No. 2002-514966 (JP-T-2002-514966) and Japanese UnexaminedPatent Application Publication No. 2008-000746 (JP-A-2008-00746)disclose air purification devices that have a metal oxide catalystcarried on the surfaces of radiators or fins, which are exposed to airflow during traveling. According to these prior arts, the ozonedestruction catalyst layer on the surface of the radiator allowsdecomposition of ozone in air.

Japanese Unexamined Patent Application Publication No. 2014-024027(JP-A-2014-024207) also discloses an air purification device that usesnot only a metal oxide catalyst but also an activated carbon for ozonedecomposition.

Technical Problem

Thus, the air purification devices for vehicle have been developed.These air purification devices have radiators or fins with surfacescarrying a catalyst for decomposing ozone in air and thus enables ozonein air to be decomposed.

Unfortunately, the NMOG credit is provided in accordance withperformance to decompose ozone after a long period of use and requirescars with the air purification devices to check the performance todecompose ozone and have on-board diagnostics. Thus, the cars having theair purification devices are expensive. Further, the amount of the ozonedecomposition catalyst carried on the surfaces of radiators or fins arelimited to allow the radiators or the fins to have high heat exchangeperformance. This results in finite performance to decompose ozone.

In Japan inspired by other countries employing NMOG credit and airpollutant control, there is a desire to develop environmentally friendlycars. The conversion of paint from solvent-based with high-VOC towater-based with low-VOC has increased. An example of the paint includesanticorrosive paint, which is coated on the surfaces of substrate suchas sheet steel of car bodies. Such a paint is applied to a wide range ofthe surfaces of car bodies. Thus, the paint may be of ozonedecomposition performance to permit the car with the paint to be moreenvironmentally friendly.

It is an object of the present invention to provide a water-based paintcomposition having performance to decompose ozone.

Solution to Problem

A water-based paint composition according to a first aspect of thepresent invention includes a manganese oxide-based catalyst, anactivated carbon, a polyacrylate-based dispersant, a water-solubleresin, a pH adjuster, and a water-based solvent.

The manganese oxide-based catalyst is required to have catalyticdecomposition of ozone. As the manganese oxide-based catalyst, metaloxides such as manganese oxides and manganese dioxides are employed.Manganese dioxides are especially preferred.

As the activated carbon, for example, a coconut shell activated carbon,a petroleum pitch-based activated carbon, or a wood-based activatedcarbon, may be employed to provide a high specific surface area forozone adsorption. Among these, an activated carbon from coconut shell isespecially preferred. The activated carbon preferably has a mediandiameter in a range of 1 to 20 μm and a specific surface area in a rangeof 500 to 3000 m²/g determined by the Brunauer-Emmett-Teller (BET)method. The median diameter may be comparable to an average particlesize. The activated carbon with very small particles tends toagglomerate or flocculate readily and thus may be less likely to bedispersed. The activated carbon with very large particles has a lowsurface area and thus may fail to provide intended performance todecompose ozone. The activated carbon with very large particles may alsofail to provide the paint film having intended film-forming andadhesion. The activated carbon with a very high surface area tends toagglomerate or flocculate readily and thus may be less likely to bedispersed. The activated carbon with a very low surface area may fail toprovide intended performance to decompose ozone and fail to provide thepaint film having intended film-forming and adhesion. The particulateactivated carbon having a median particle diameter in a range of 1 to 20μm and a specific surface area in a range of 500 to 3000 m²/g determinedby the BET method is excellent in dispersion and dispersion stability,and has high performance to decompose ozone. The most preferred medianparticle diameter is in a range of 3 to 18 μm, especially, in a range of5 to 15 μm. The most preferred specific surface area by the BET methodis in a range of 600 to 2500 m²/g, especially, in a range of 900 to 2000m²/g.

The “specific surface area” is determined by the Brunauer-Emmett-Teller(BET) method. According to BET method, the volume of gas such asnitrogen adsorbed to the surface of the target particles is measured atthe boiling point of liquid-nitrogen. The specific surface area isdetermined by physical adsorption of the gas on the surface of thetarget particles and by calculating the amount of adsorbate gascorresponding to a monomolecular layer on the surface.

The “median diameter” is a particle size (diameter) at a point where 50%(by weight or number) of the particles resides above this point and 50%(by weight or number) of the particles resides below this point inparticle size distributions, according to “Test Powders and TestParticles” designated by Japanese Industrial Standards (JIS) Z 8901.

The “median diameter” is also called 50% particle size, 50% diameter, orD50. Average particle diameter may be often used as representation of aparticle size, as well as a median diameter. Herein, the median diameteris measured by laser diffraction/scattering analysis. Alternatively, thevalue of the median diameter may be disclosed in product description.The “median diameter measured by laser diffraction/scattering analysis”is a particle diameter (D50) that is the midpoints or 50% position ofthe cumulative % distribution determined by laser diffraction/scatteringanalysis with a laser diffraction particle size analyzer. With respectto the value of the particle diameter, approximate value or any error inmeasurement is acceptable. Errors of 10% or less is within an allowablerange. When the particle size distribution is often symmetrical aboutthe center (50% diameter), the median diameter is the same as theaverage particle diameter. From this point of view, the median diametercan be loosely equated with the average particle diameter. Thedifference between the median diameter and the average particle diametermay be considered to be within an error range.

The water-soluble resin may be also called a water-dispersible resin.

The pH adjuster is used to adjust the hydrogen-ion export (pH) to,preferably, in a range of 7 to 12, more preferably, 9.5 to 11. The pHadjuster may be also called a neutralizer.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst is preferablya manganese dioxide-based catalyst.

The manganese dioxide-based catalyst preferably has a median diameter ina range of 1 to 20 μm and a specific surface area in a range of 100 to400 m²/g determined by the BET method. The median diameter may becomparable to an average particle size. The catalyst with very smallparticles tends to agglomerate or flocculate readily and thus may beless likely to be dispersed. The catalyst with very large particles hasa very low surface area and thus may fail to provide intendedperformance to decompose ozone. Additionally, the catalyst with verylarge particles may fail to provide the paint film having intendedfilm-forming and adhesion. The catalyst with a very large surface areatends to agglomerate or flocculate readily and thus may be less likelyto be dispersed. The catalyst with a very low surface area may fail toprovide intended performance to decompose ozone and fail to provide thepaint film having intended film-forming and adhesion. The particulatecatalyst having a median diameter in a range of 1 to 20 μm and aspecific surface area in a range of 100 to 400 m²/g determined by theBET method is excellent in dispersion and dispersion stability, and hashigh performance to decompose ozone. The most median diameter is in arange of 3 to 18 μm, especially, in a range of 5 to 15 μm. The mostpreferred specific surface area determined by the BET method is in arange of 150 to 350 m²/g, especially, in a range of 180 to 300 m²/g.

In the water-based paint composition according to the first aspect ofthe present invention, the weight ratio of the manganese oxide-basedcatalyst to the activated carbon (solid content) is preferably in therange of 20:80 to 80:20, more preferably, 30:70 to 70:30.

The weight ratio means solid weight ratio. The manganese oxide-basedcatalyst and the activated carbon are mixed at the weight ratio in arange of, preferably, 20:80 to 80:20, more preferably, 30:70 to 70:30 toprovide the paint film having the weight ratio of the manganeseoxide-based catalyst to the activated carbon in a range of, preferably,20:80 to 80:20, more preferably, 30:70 to 70:30.

In the water-based paint composition according to the first aspect ofthe present invention, the total amount of the manganese oxide-basedcatalyst and the activated carbon in the paint film from the water-basedpaint composition is preferably in a range of 60 to 90%, morepreferably, 65 to 85%, most preferably, 70 to 80% by mass.

In the water-based paint composition according to the first aspect ofthe present invention, the polyacrylate-based dispersant preferably hasa weight average molecular in a range of 5000 to 30000, more preferably,6000 to 28000, particularly, 7000 to 25000, acid value in a range of 1to 50, more preferably, 3 to 48, most preferably, 5 to 45, andhydrogen-ion exponent (pH) in a range of 4 to 9, more preferably, 4.5 to8.5, most preferably, 5 to 8. The weight average molecular is determinedby gel permeation chromatography (GPC) relative to polystyrene standard.

In the water-based paint composition according to the first aspect ofthe present invention, the polyacrylate-based dispersant is preferablypresent at 1.5 to 75, more preferably, 2 to 60, particularly, 2.5 to 50parts by mass, per hundred parts by weight of the total solid amount ofthe manganese oxide-based catalyst and the activated carbon.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst and theactivated carbon preferably have a maximum particle diameter (D_(max))of 20 μm or less. The maximum particle diameter, which is indicative ofparticle dispersion, is determined by a line transect method with agrind gauge according to JIS K 5600 and JIS K 5400 (1990).

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst and theactivated carbon preferably have a 90% diameter (D90) of 10 μm or less.The 90% diameter (cumulative %) is based on a volume distribution and isdetermined by laser diffraction analysis with a laser diffractionparticle size analyzer.

In the water-based paint composition according to the first aspect ofthe present invention, the water-soluble resin is preferably an acrylicresin or a polypropylene resin.

A process for preparing a water-based paint composition according to asecond aspect of the present invention includes a dispersion step ofmixing and dispersing a water-based solvent, a manganese oxide-basedcatalyst, an activated carbon, and a polyacrylate-based dispersant, aneutralization step of mixing a pH adjuster with the resultant mixture,and a paint prepare final step of mixing a water-soluble resin with theresultant mixture.

In the process for preparing the water-based paint composition accordingto the second aspect of the present invention, the manganese oxide-basedcatalyst and the activated carbon are dispersed using a bead mill or aroll mill and have a maximum particle diameter of 20 μm or less throughthe dispersion step.

The maximum particle diameter, which is indicative of particledispersion, is determined by a line transect method with a grind gaugeaccording to JIS K 5600 and JIS K 5400 (1990).

In the process for preparing the water-based paint composition accordingto the second aspect of the present invention, the manganese oxide-basedcatalyst and the activated carbon preferably are dispersed using a beadmill or a roll mill and have a 90% diameter (D90) of 10 μm or lessthrough the dispersion step.

The 90% diameter (cumulative %) is based on a volume distribution and isdetermined by laser diffraction analysis with a laser diffractionparticle size analyzer.

With respect to the above values, approximate value or any error in usedmaterials, application use, calculation, or measurement is acceptable.

Advantageous Effects of Invention

In a first aspect of the present invention, a water-based paintcomposition includes a manganese-oxide based catalyst, an activatedcarbon, a polyacrylate-based dispersant, a water-soluble resin, a pHadjuster, and a water-based solvent. The water-based paint compositionis applied to a substrate and then dried. This yields a hardened paintfilm.

With the water-based paint composition according to the first aspect ofthe present invention, the polyacrylate-based dispersant allows themanganese oxide-based catalyst and the activated carbon to be dispersedfinely and stably. Thus, the water-based paint composition is excellentin storage stability. Additionally, the water-based paint compositioncreates the paint film having good film-forming and good adhesion. Thewater-based paint composition is less likely to create the hardenedpaint film having paint seeding. Further, the fine dispersed catalystand the fine dispersed activated carbon adsorb a large amount of ozone.Thus, the paint film from the water-based paint composition has highperformance to decompose ozone. In particular, the combination use ofthe manganese oxide-based catalyst and the activated carbon provideshigher performance to decompose ozone than if only one or the other isused.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst is preferablya manganese dioxide-based catalyst. This manganese dioxide-basedcatalyst has higher catalytic activity and provides higher performanceto decompose ozone.

In the water-based paint composition according to the first aspect ofthe present invention, the solid weight ratio of the manganeseoxide-based catalyst to the activated carbon is preferably in a range of20/80 to 80/20, more preferably, 30/70 to 70/30. Such a ratio allows themanganese oxide-based catalyst and the activated carbon to actsynergistically, thus providing higher performance to decompose ozone,as well as good storage stability.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst and theactivated carbon is preferably is present in the paint film from thewater-based paint composition at total concentration in a range of 60 to90%, more preferably, 65 to 85%, most preferably, 70 to 80% by mass.This provides higher performance to decompose ozone, as well as highadhesion to substrates.

In the water-based paint composition according to the first aspect ofthe present invention, the polyacrylate-based dispersant preferably hasa weight average molecular in a range of 5000 to 30000, an acid value ina range of 1 to 50, and a hydrogen-ion exponent in a range of pH4 topH9. This water-based paint composition has the paint contents withhigher dispersion and dispersion stability, as well as performance todecompose ozone.

In the water-based paint composition according to the first aspect ofthe present invention, the polyacrylate-based dispersant is preferablypresent at 1.5 to 75, more preferably, 2 to 60, particularly, 2.5 to 50parts by mass, per hundred parts by weight of the total solid amount ofthe manganese oxide-based catalyst and the activated carbon. Thiswater-based paint composition has both high storage stability and highperformance to decompose ozone.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst and theactivated carbon have a maximum particle diameter (D_(max)) of 20 μm orless. The maximum particle diameter, which is indicative of particledispersion, is determined by a line transect method with a grind gaugeaccording to JIS K 5600 and JIS K 5400 (1990).

The inventors have found that the use of the polyacrylate-baseddispersant allows the manganese oxide-based catalyst and the activatedcarbon to be finely dispersed and have a maximum particle diameter of 20μm or less, which is determined by a line transect method with a grindgauge according to JIS K 5600 and JIS K 5400 (1990). The water-basedpaint composition including the manganese oxide-based catalyst and theactivated carbon that have a maximum particle diameter of 20 μm or less,which is determined by a line transect method with a grind gaugeaccording to JIS K 5600 and JIS K 5400 (1990), has less agglomeration orflocculation of the paint contents including the activated carbon andthe catalyst. Thus, this water-based paint composition provides thepaint film having higher forming-film and adhesion. Additionally, themanganese oxide-based catalyst and the activated carbon that have amaximum particle diameter of 20 μm or less adsorb a larger amount ofozone, thus providing higher performance to decompose ozone. Further,this water-based paint composition is excellent in dispersion stabilityand storage stability. Thus, this water-based paint composition has longshelf life and provides the paint film with stable paint performance.

In the water-based paint composition according to the first aspect ofthe present invention, the manganese oxide-based catalyst and theactivated carbon have a 90% diameter (D90) of 10 μm or less. The 90%diameter (cumulative %) is based on a volume distribution and isdetermined by laser diffraction analysis.

The inventors have found that the use of the polyacrylate-baseddispersant allows the manganese oxide-based catalyst and the activatedcarbon to be finely dispersed and have a 90% diameter (D90) of 10 μm orless, which is determined by laser diffraction analysis. The water-basedpaint composition including the manganese oxide-based catalyst and theactivated carbon that have a 90% diameters (D90) of 10 μm or less has asmall amount of coarser grains such as agglomeration and flocculation.Thus, this water-based paint composition provides the paint film havingless paint seeding and evenness. This paint film is excellent informing-film and adhesion. Additionally, the paint film having lessagglomeration and flocculation adsorbs a large amount of ozone and havehigh performance to decompose ozone. Further, this water-based paintcomposition is excellent in dispersion stability and storage stability.

Thus, this water-based paint composition has higher storage stability,and the paint film from the paint composition is excellent in visualappearance and has higher performance to decompose ozone.

In the water-based paint composition according to the first aspect ofthe present invention, the water-based resin is preferably an acrylicresin or a polypropylene resin. The acrylic resin and the polypropyleneresin are compatible with the manganese oxide-based catalyst and theactivated carbon. Thus, the manganese oxide-based catalyst and theactivated carbon is more uniformly dispersed in the resin. Consequently,this water-based paint composition has the paint contents with higherdispersion and dispersion stability. In particular, the acrylic resinhas a wide variety of a molecular weight. Thus, the use of the acrylicresin may easily yield the paint film having desired performance.Additionally, the acrylic resin provides the paint film having highweather resistance, water resistance, and chemical resistance. Thepolypropylene resin provides the paint film having good adhesion toresin substrates in addition to metal substrates. Such a paint film haslong-term high performance to decompose ozone.

In a second aspect of the present invention, a process for preparing awater-based paint composition includes the successive steps of: mixing awater-based solvent, a manganese oxide-based catalyst, an activatedcarbon, and a polyacrylate-based dispersant; mixing a pH adjuster withthe resultant mixture for neutralization; and mixing a water-solubleresin with the resultant mixture. With the process for preparing thewater-based paint composition according to the second aspect of thepresent invention, the polyacrylate-based dispersant allows themanganese oxide-based catalyst and the activated carbon to be dispersedfinely and stably. Thus, the water-based paint composition is excellentin storage stability. This water-based paint composition is applied to asubstrate and then dried. This yields a hardened paint film with paintseeding free. Such a paint film has good film-forming and good adhesion.The fine dispersed catalyst and the fine dispersed activated carbon inthe paint film adsorb a large amount of ozone. Thus, the paint film hashigh performance to decompose ozone. In particular, the combination useof the manganese oxide-based catalyst and the activated carbon provideshigher performance to decompose ozone than if only one or the other isused.

In the process for preparing the water-based paint composition accordingto the second aspect of the present invention, the manganese oxide-basedcatalyst and the activated carbon are dispersed using a bead mill or aroll mill, and have a maximum particle diameter of 20 μm or less througha dispersion step.

The inventors have found that the use of the polyacrylate-baseddispersant allows the manganese oxide-based catalyst and the activatedcarbon to be finely dispersed and have a maximum particle diameter of 20μm or less, which is determined by a line transect method with a grindgauge. The water-based paint composition including the manganeseoxide-based catalyst and the activated carbon that have a maximumparticle diameter of 20 μm or less, which is determined by a linetransect method with a grind gauge, has less agglomeration orflocculation of the paint contents including the activated carbon andthe catalyst. Thus, this water-based paint composition provides thepaint film having higher forming-film and adhesion. Additionally, themanganese oxide-based catalyst and the activated carbon that have amaximum particle diameter of 20 μm or less adsorb a larger amount ofozone, thus providing higher performance to decompose ozone. Further,this water-based paint composition is excellent in dispersion stabilityand storage stability.

Thus, the water-based paint composition has long shelf life and thepaint film from the water-based paint composition has stable paintperformance.

In the process for preparing the water-based paint composition accordingto the second aspect of the present invention, the manganese oxide-basedcatalyst and the activated carbon are dispersed using a bead mill or aroll mill, and have 90% diameters (D90) of 10 μm or less through adispersion step. The 90% diameter (cumulative %) is based on a volumedistribution and is determined by laser diffraction analysis.

The inventors have found that the use of the polyacrylate-baseddispersant allows the manganese oxide-based catalyst and the activatedcarbon to be finely dispersed and a 90% diameter (D90) of 10 μm or less,which is determined by laser diffraction analysis. The water-based paintcomposition including the manganese oxide-based catalyst and theactivated carbon that have a 90% diameters (D90) of 10 μm or less has asmall amount of coarser grains such as agglomeration and flocculation.Thus, this water-based paint composition provides the paint film havingless paint seeding and evenness. Such a paint film is excellent informing-film and adhesion. Additionally, the paint film having lessagglomeration and flocculation adsorbs a large amount of ozone and havehigh performance to decompose ozone. Further, this water-based paintcomposition is excellent in dispersion stability and storage stability.

Thus, the water-based paint composition has higher storage stability andthe paint film from the composition is excellent in visual appearanceand higher performance to decompose ozone.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating the ozone decomposition test forexamples of TABLE 1, TABLE 2, and TABLE 4.

FIG. 2 is a schematic view illustrating the ozone decomposition test forexamples of TABLE 3.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described hereafter. In theembodiments of the present invention, the same marks and the same codesmean the same or equivalent function parts. Thus, overlapped descriptionthereof will be omitted here.

A process for preparing a water-based paint composition according to anembodiment of the present invention will first be described.

The water-based paint composition according to the embodiment of thepresent invention includes a manganese oxide-based catalyst, anactivated carbon, a polyacrylate-based dispersant, a water-solubleresin, a pH adjuster, and water as a solvent.

To prepare the water-based paint composition according to the embodimentof the present invention, a dispersing step is first performed. In thisdispersing step, water as a solvent, a manganese oxide-based catalyst,an activated carbon, and a polyacrylate-based dispersant are mixed andthe resultant mixture is dispersed using a disperser.

As the manganese oxide-based catalyst (Mn_(x)O_(y)-based catalyst), amanganese oxide such as a manganese monoxide-based catalyst (MnO-basedcatalyst), a manganese dioxide-based catalyst or a manganese (IV)oxide-based catalyst, a spinel metal manganese oxide, or the like may beemployed. Among these, a manganese dioxide-based catalyst (MnO₂-basedcatalyst), which has high catalytic activity, is especially preferred.Manganese dioxide is substantially non-stoichiometric compound with theformula MnO_(x) (X=1.93-2).

The manganese dioxide may be natural or synthetic, specifically producedusing electrolysis technique or chemical synthesis technique. Themanganese dioxide may have an amorphous structure or crystal structuresuch as α-type, β-type, γ-type, or δ-type structure. Among thesestructures, a α-manganese dioxide with a cryptomelane structure isespecially preferred. Alternatively, the manganese dioxide may have anamorphous structure.

The manganese dioxide-based catalyst, which includes a manganese dioxide(MnO₂) as a main component, may include NiO, CuO, or AgO as aco-catalyst. The manganese dioxide content is preferably 70% or more,most preferably, 80% or more in the manganese dioxide-based catalyst.

The manganese oxide-based catalyst such as a manganese dioxide-basedcatalyst preferably has a specific surface area in a range of 100 to 400m²/g, which is determined by the Brunauer-Emmett-Teller (BET) method orthe nitrogen adsorption method. The particulate catalyst having too higha specific surface area may agglomate or flocculate easily, and be lesslikely to be dispersed. Poor dispersion of the particulate catalyst maycause a paint nozzle to be clogged with the catalyst particles, orprovide the paint film having paint seeding or agglomerate. The paintfilm with paint seeding or agglomerate may have poor film-forming oradhesion. Such a paint film may peel easily or the catalyst particlesmay drop from the paint film easily. Further, poor dispersion stabilityof the particulate catalyst may fail to provide intended storagestability of the paint composition. The particulate catalyst having toolow a specific surface area may fail to provide intended performance todecompose ozone. The catalyst particles having a specific surface areain a range of 100 to 400 m²/g, which is determined by the BET method, iswell dispersed and excellent in dispersion stability. Additionally, sucha particulate catalyst provides the paint film having excellentfilm-forming and adhesion. Such a paint film is less likely to drop thecatalyst particles and achieves high performance to decompose ozone fora long term. Further, the particulate catalyst having a specific surfacearea in a range of 100 to 400 m²/g provides the paint composition withhigher storage stability of. A most preferred specific surface areadetermined by the BET method is in a range of 150 to 350 m²/g,especially, 180 to 300 m²/g.

The manganese oxide-based catalyst such as a manganese dioxide-basedcatalyst preferably has a median diameter in a range of 1 to 20 μm. Themedian diameter may be comparable to an average particle size. Theparticulate catalyst having too large a particle size has a low surfacearea and thus may fail to achieve intended performance to decomposeozone. The particulate catalyst having too large a particle size mayprovide the paint film having poor film-forming or adhesion. Such apaint film may peel easily or the catalyst may drop from the paint filmeasily. The particulate catalyst having too small a particle size mayagglomerate or flocculate easily and be less likely to be dispersed.Poor dispersion of the particulate catalyst may provide the paint filmhaving paint seeding or agglomerate. The paint film with paint seedingor agglomerate may have poor film-forming or adhesion. Such a paint filmmay peel easily or the catalyst particles may drop from the paint filmeasily. Further, poor dispersion stability of the particulate catalystmay fail to provide intended storage stability of the paint composition.The particulate catalyst having a median diameter in a range of 1 to 20μm is well dispersed and excellent in dispersion stability.Additionally, such a catalyst provides the paint film having excellentfilm-forming and adhesion. Such a paint film is less likely to drop thecatalyst and achieves high performance to decompose ozone for a longterm. Further, the particular catalyst having a median diameter in arange of 1 to 20 μm provides the paint composition with higher storagestability. A most preferred median diameter is in a range of 3 to 18 μm,especially, 5 to 15 μm.

The manganese oxide-based catalyst enables ozone to be decomposed intoharmless substance(s). Specifically, the catalyst adsorbs ozone anddecreases self-decomposition reaction activation energy of the ozone.This results in ozone decomposition. The resulting decomposition productare desorbed from the catalyst. Thus, the ozone is decomposed intooxygen through the catalysis of the manganese oxide-based catalyst.

Examples of the activated carbon include sawdust, wood chip, charcoal,bamboo charcoal, coal (including lignite, brown coal, and bituminouscoal), petroleum such as petroleum pitch or oil carbon, walnut shellcharcoal, coconut shell charcoal, resin (including phenolic resin andepoxy resin), and rayon. Among these, preferred are coconut shellcharcoal from coconut palm, oil palm, sago palm, which are high incarbon content. The activated carbon preferably has a carbon content of90% or more.

The activated carbon such as a coconut shell charcoal preferably has aspecific surface area in a range of 500 to 3000 m²/g, which isdetermined by the BET method using nitrogen adsorbate. The activatedcarbon having too high a specific surface area may agglomerate orflocculate easily and be less likely to be dispersed. Poor dispersion ofthe activated carbon may cause a paint nozzle to be clogged with theactivated carbon particles, or provide the paint film having paintseeding or agglomerate. The paint film with paint seeding or agglomeratemay have poor film-forming or adhesion. Such a paint film may peeleasily or the activated carbon particles may drop from the paint filmeasily. Further, poor dispersion stability of the particulate activatedcarbon may fail to provide intended storage stability of the paintcomposition. The activated carbon having too low a specific surface areamay fail to provide intended performance to decompose ozone. Theactivated carbon having a specific surface area in a range of 500 to3000 m²/g, which is determined by the BET method, is well dispersed andexcellent in dispersion stability. Additionally, such a particulateactivated carbon provides the paint film having excellent film-formingand adhesion. Such a paint film is less likely to drop the activatedcarbon particles and achieves high performance to decompose ozone for along term. Further, the particular activated carbon having a specificsurface area in a range of 500 to 3000 m²/g provides the paintcomposition with higher storage stability. A most preferred specificsurface area determined by the BET method is in a range of 600 to 2500m²/g, especially, in a range of 900 to 2000 m²/g. The activated carbonhas a total pore volume, for example, in a range of 0.1 to 1.5 cm³/g,preferably, 0.2 to 1.0 cm³/g. This total pore volume is determined inaccordance with nitrogen adsorption amount at relative pressure P/P₀ of1.0 in nitrogen adsorption isotherm. The activated carbon has an averagepore diameter (which is calculated using the formula: total porevolume/BET specific surface area×4), for example, in a range of 0.3 to10 nm, preferably, 0.5 to 5 nm, for preventing particulate matters inair from being bound to the activated carbon and providing higherperformance to adsorb ozone.

The activated carbon such as a coconut shell charcoal preferably has amedian diameter in a range of 1 to 20 μm. The median diameter may becomparable to an average particle size. The particulate activated carbonhaving too large a particle size has a low surface area and thus mayfail to achieve high performance to decompose ozone. The particulateactivated carbon having too large a particle size may provide the paintfilm having poor film-forming or adhesion. Such a paint film may peeleasily or the activated carbon may drop from the paint film easily. Theparticulate activated carbon having too small a particle size mayagglomerate or flocculate easily and be less likely to be dispersed.Poor dispersion of the particulate activated carbon may provide thepaint film having paint seeding or agglomerate. The paint film withpaint seeding or agglomerate may have poor film-forming or adhesion.Such a paint film may peel easily or the activated carbon particles maydrop from the paint film easily. Further, poor dispersion stability ofthe particulate activated carbon may fail to provide intended storagestability of the paint composition. The activated carbon particleshaving a median diameter in a range of 1 to 20 μm is well dispersed andexcellent in dispersion stability. Additionally, such a particulateactivated carbon provides the paint film having excellent film-formingand adhesion. Such a paint film is less likely to drop the activatedcarbon particles and achieves high performance to decompose ozone for along term. A most preferred specific surface area is in a range of 3 to18 μm, especially, in a range of 5 to 15 μm.

The activated carbon has pores in which ozone is adsorbed. The ozoneadsorbed on the activated carbon reacts with the activated carbon orreceives electrons from the activated carbon; that is, the activatedcarbon adsorbs ozone and decreases self-decomposition reactionactivation energy of the ozone. This causes the ozone to be decomposedinto carbon monoxide, carbon dioxide, reactive oxygen species, oroxygen. Thus, the ozone is decomposed into harmless substance(s). Theactivated carbon exhibits higher activity in a wide range oftemperatures including room temperature (15° C. to 25° C.) and in a widerange of humidity, while the manganese oxide-based catalyst exhibitshigher activity at high temperatures, for example, about 80° C.

Thus, the water-based paint composition of the present embodimentincludes a manganese oxide-based catalyst such as a manganesedioxide-based catalyst and an activated carbon such as a coconut shellcharcoal. This yields the paint film having high performance todecompose ozone. In particular, the water-based paint composition of thepresent embodiment includes both a manganese oxide-based catalyst and anactivated carbon. Such a water-based paint composition has higherperformance to decompose ozone compared to a composition including oneof a manganese oxide-based catalyst or an activated carbon. This may bebecause the heat of reaction between the activated carbon and the ozonemay increase the catalytic activity of the manganese oxide-basedcatalyst. Alternatively or additionally, the reason may be thatcombination use of the manganese oxide-based catalyst and the activatedcarbon may allow ozone decomposition over a wider range of temperatures.Alternatively, the reason may be that the manganese oxide-based catalystparticles may be held in the pores of the activated carbon particles andthis may increase the frequency of contact with the ozone. Further, thereason may be that the manganese oxide-based catalyst may preventoxidation or degradation of the activated carbon, which is exposed toreactive oxygen species. For such reasons, the water-based paintcomposition including both a manganese oxide-based catalyst and anactivated carbon has higher performance to decompose ozone compared to acomposition including one of a manganese oxide-based catalyst or anactivated carbon.

The water-based paint composition is required to have long term storageor storage stability for practical use. Here, the use of only theactivated carbon for decomposing ozone fails to provide intended storagestability. This is because the activated carbon, which has adsorptionproperties, adsorbs organic matters such as resin in the paintcomposition and thus results in agglomeration or flocculation. Thus, thewater-based paint composition of the present embodiment includes boththe activated carbon and the manganese oxide-based catalyst fordecomposing ozone. This combination enables the paint composition tohave both high performance to decompose ozone and high storagestability. Additionally, the combination enables the paint compositionto have a longer shelf life than if a paint composition uses only theactivated carbon.

A paint composition uses only the manganese oxide-based catalyst mightbe expensive. Whereas, the paint composition using both the manganeseoxide-based catalyst and the activated carbon, which is available at lowcost, is inexpensive.

The manganese oxide-based catalyst (hereinafter, referred to as“catalyst”) and the activated carbon, which have performance todecompose ozone, are provided in powder or particulate form. To preparethe paint having intended liquidity suitable for application, thepowdery or particulate catalyst and the powdery or particulate activatedcarbon are required to be uniformly dispersed in the paint including aresin and a solvent. Whereas, the catalyst and the activated carbon,which have a high specific surface area for adsorbing a large amount ofozone, is easily agglomerate or flocculate. In particular, the activatedcarbon is more easily agglomerate or flocculate because the paintcontents including organic matters such as a resin or a catalyst areheld in the pores of the particulate activated carbon. A large amount ofthe agglomerate or flocculate of the catalyst and the activated carbon,which are poorly dispersed, may cause gelation and viscosity increase ofthe paint composition. Additionally, the agglomerate or flocculate mayclog an applicator including a pipe and a pump. Thus, with a largeamount of the agglomerate or flocculate of the catalyst and theactivated carbon, the paint composition may fail to provide intendedliquidity suitable for application. Further, the paint film from such apaint composition may have paint seeding and roughness. Thus, the paintfilm may be required to be thick to hind a target surface adequately.Such a paint film shows poor film-forming, adhesion, and appearance.Furthermore, a large amount of the agglomerate or flocculate may failprovide intended performance to adsorb and decompose ozone. In addition,the gelation and viscosity increase caused by a large amount of theagglomeration or flocculation, which are poorly dispersed, provides poorstorage stability of the paint composition. Such a paint composition isshort shelf life. Thus, to prepare the paint having intended liquiditysuitable for application, the powdery or particulate catalyst and thepowdery or particulate activated carbon are required to be preventedfrom agglomerating or flocculating and to be well dispersed.

The inventors have found that polyacrylate-based dispersant prevents theagglomeration or flocculation of the catalyst and the activated carbon.That is, the inventors have found that the polyacrylate-based dispersantenables the particulate catalyst and the particulate activated carbon tobe finely and stably dispersed in the paint.

The present embodiment includes a dispersion step. In the dispersionstep, the catalyst, the activated carbon, water such as the deionizedwater as a solvent, and the polyacrylate-based dispersant, which enablesthe catalyst and the activated carbon to be well dispersed, are mixedand stirred to disperse the contents using a mixing and dispersionmachine.

This prevents the agglomeration or flocculation of the catalyst and theactivated carbon and enables the catalyst and the activated carbon to bewell and stably dispersed. That is, the catalyst and the activatedcarbon are finely dispersed. This yields the particulate catalyst havinga maximum particle diameter (D_(max)) of, for example, 20 μm or less andthe particulate activated carbon having a maximum particle diameter of,for example, 20 μm or less. The maximum particle diameter is determinedby a line transect method with a grind gauge on the basis of JISK 5600and JISK 5400 (1990). Additionally, the catalyst and the activatedcarbon have 90% (by weight or number) particle size (D90) of, forexample, 10 μm or less. The cumulative 90% particle size (D90 or 90%diameter), is determined by laser diffraction analysis with a laserdiffraction particle size analyzer. Such a water-based paintcomposition, in which the catalyst and the activated carbon are finelydispersed, is less likely to creates paint seeding and roughness in thepaint film. Thus, this paint film is excellent in film-forming andadhesion to a target substrate. Additionally, the catalyst and theactivated carbon that are finely dispersed adsorb a large amount ofozone. Thus, the paint film has high performance to decompose ozone.Furthermore, this paint film has a flat surface and good appearance.Moreover, the polyacrylate-based dispersant prevents the agglomerationor flocculation of the catalyst and the activated carbon, and enablesthe catalyst and the activated carbon to be well and stably dispersed.Thus, the water-based paint composition exhibits good storage stabilityand long shelf life.

Examples of the polyacrylate-based dispersant, which enables thecatalyst and the activated carbon to be well dispersed, includes apolyacrylate salt and a compound with an acrylic group or a modifiedacrylic group. The polyacrylate-based dispersant may be a modifiedacrylic polyacrylate-based dispersant.

The polyacrylate-based dispersant preferably has a weight-averagemolecular weight in a range of 5000 to 30000. The polyacrylate-baseddispersant having a high molecular weight has many affinity bindingsites in the molecular. Thus, such a polyacrylate-based dispersantadsorbs a large amount of the particulate catalyst and the particulateactivated carbon and thus prevents agglomeration or flocculation of thecatalyst and the activated carbon even when the polyacrylate-baseddispersant is present at a low concentration. However, thepolyacrylate-based dispersant having too high a molecular weight haspoor compatibility with or affinity for the paint contents. Thus, such apolyacrylate-based dispersant may fail to provide intended paintperformance. The polyacrylate-based dispersant having too low amolecular weight has a few affinity binding sites and may fail toprovide intended performance to disperse the catalyst and the activatedcarbon. The high content of the polyacrylate-based dispersant canprovide high performance to disperse the catalyst and the activatedcarbon. However, the high content of the polyacrylate-based dispersantmay fail to provide intended performance to decompose ozone because thehigh content of the polyacrylate-based dispersant may cause ozone tofail to adsorb onto the catalyst and the activated carbon. Thepolyacrylate-based dispersant having a weight-average molecular weightin a range of 5000 to 30000 has compatibility with or high affinity forthe paint contents and allows the catalyst and the activated carbon tobe highly dispersed. A preferred weight-average molecular weight of thepolyacrylate-based dispersant is in a range of 6000 to 28000, morepreferably, 7000 to 25000.

The polyacrylate-based dispersant preferably has an acid value in arange of 1 to 50. The polyacrylate-based dispersant having too high anacid value may fail to provide an intended adsorption property dependingon the polarity of the paint content such as an additive including apigment. The polyacrylate-based dispersant preferably has a hydrogen-ionexponent in a range of pH4 to pH9. The hydrogen-ion exponent of thepolyacrylate-based dispersant less or more than these values may providepoor dispersion of the paint contents, depending on an additive such asa pigment. The polyacrylate-based dispersant having a hydrogen-ionexponent in a range of pH4 to pH9 provides intended dispersion stablyregardless of the paint contents. A preferred acid value is in a rangeof 3 to 48, more preferably, 5 to 45. A preferred hydrogen-ion exponentis in a range of pH4.5 to pH8.5, more preferably, pH5 to pH8.

As the polyacrylate-based dispersant, commercial items, for example,DESPERBYK from BYK-Chemie, EFKA from Ciba Specialty Chemicals or EFKAADDITIVES B.V., DISPARLON of Kusumoto Chemicals, Ltd., or SN-thickenerfrom SANNOPKO may be employed.

Thus, the polyacrylate-based dispersant allows the catalyst and theactivated carbon to be stably dispersed. This may be because thepolyacrylate-based dispersant may attract the catalyst and the activatedcarbon through electric repulsion. This dispersant attraction mayprevent the agglomeration or flocculation of the catalyst and enablesthe activated carbon and the catalyst to have a fine particle size.Alternatively or additionally, steric effects of anchor or polymer chainof the polyacrylate-based dispersant may prevent the agglomeration orflocculation of the catalyst and the activated carbon and enables theactivated carbon and the catalyst to have a fine particle size. Inparticular, the polyacrylate-based dispersant has a high molecularweight and has many affinity binding sites. Thus, even a small amount ofthe polyacrylate-based dispersant achieves intended performance to bindthe catalyst and the activated carbon and enables the catalyst and theactivated carbon to be well dispersed. A large amount of thepolyacrylate-based dispersant is not required to disperse the catalystand the activated carbon well. Thus, the polyacrylate-based dispersantis unlikely to inhibit ozone binding to the catalyst and the activatedcarbon.

As the mixing and dispersion machine used in the dispersion step, forexample, a ball mill, bead mill, high pressure injector, dissolver,banbury mixer, planetary mixer, butterfly mixer, spiral mixer, rollmill, sand mill, paint shaker, glen mill, high speed impeller mill, openkneader, vacuum kneader, attritor, high speed disperser, homo mixer,homogenizer, colloid mill, microfluidizer, sonolator, and cavitron maybe employed. Among these, the tbead mill or roll mill are preferred. Thebead mill and roll mill allow the catalyst and the activated carbon tobe finely dispersed with low energy.

The dispersed mixtures of the catalyst, the activated carbon, the water,and the polyacrylate-based dispersant are then mixed with a pH adjusteror a neutralizer in a neutralization step.

The pH adjuster is required to neutralize the mixture obtained in thedispersion step and adjust the pH to, for example, 7-12. As the pHadjuster, for example, a low-boiling-point amine including triethylamine(TEA), ammonia, and dimethylaminoethanol are employed. The pH of themixtures is adjusted to in a range of pH7 to pH12, preferably, in arange of pH8 to pH11.5, more preferably, in a range of pH9.5 to pH11with the pH adjusters in the neutralization step. This prevents decreaseof the paint viscosity and settling of the paint contents. Thus, thepaint contents are uniformly and stably dispersed. The paint film fromthe paint composition in which the paint contents are uniformly andstably dispersed has less variation in performance.

The mixture obtained in the neutralization step are then mixed with awater-soluble resin in a paint prepare final step. If necessary, apigment or an additive is added to them. The mixtures are stirred with,for example, a disperser.

The water-soluble resin, which is primary content of the paint, may bealso called a water-dispersible resin. As the water-soluble resin, forexample, an epoxy resin, epoxy ester resin, polyester resin, acrylicresin including methacrylate resin, acrylic silicone resin, polyurethaneresin, alkyd resin, urethane resin, vinyl resin, urea formaldehyderesin, styrene butadiene rubber (SBR), and nitrile butadiene rubber(NBR) may be employed. These may be used individually or two or more maybe used in combination. The water-soluble resin is provided in anaqueous solution, a emulsion, or a dispersion form.

The term “emulsion” inherently means liquids including colloidalparticles or larger particles than colloidal particles are dispersed inliquids. This is referred to clause 152 of Iwanami Physics and ChemistryDictionary, the fifth edition edit by Saburo Nagakura, published byIwanami Shoten Publishing Ltd., at 20 Feb. 1998. However, herein, theterm “emulsion” has broad meaning; that is, it means both liquids aredispersed in liquids and solids are suspended in liquids.

A preferred water-soluble resin is an acrylic resin or a polypropyleneresin for providing advantageous dispersion, weather resistance, cost,adhesion, dispersion stability, and affinity to the catalyst and theactivated carbon. The acrylic resin has high adhesion to metal. Thepolypropylene resin has high adhesion to both metal and resin.

The acrylic resin is also known as methacrylic resin. The acrylic resin,which is derived from acrylic acid or methacrylic acid, may be(meth)acrylate ester homopolymer, (meth)acrylate ester copolymer.Examples of (meth)acrylate ester includes the methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate,hexyl (meth)acrylate, ethyl hexyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, 3-hydroxybutyl(meth)acrylate, 2,2-bis(hydroxymethyl)ethyl (meth)acrylate,3-chloro-2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate,aminoethyl (meth)acrylate, aminopropyl (meth)acrylate,(dimethylamino)ethyl (meth)acrylate, (diethylamino)ethyl (meth)acrylate,methoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl(meth)acrylate, and stearyl (meth)acrylate.

A monomer that can be copolymerized with the (meth) acrylic acidpreferably has an ethylenically unsaturated group. Examples of themonomer include ethylene, propylene, butylene, butadiene, styrene,α-methylstyrene, vinylphenol, vinyl chloride, vinylidene chloride, vinylacetate, vinyl pivalate, vinyl benzoate, vinyl alcohol, allyl alcohol,crotonic acid, itaconic acid, maleic acid, fumaric acid, (meth)acrylamide, N-methylolacrylamide, N-(butoxymethyl) (meth) acrylamide,and (meth) acrylonitrile.

Copolymerization is common in emulsion polymerization. However, it isnot limited. Acid may include alkali metal salts or alkali earth metalsalts. Alternatively, urethane modified (meth) aclylic resin, epoxymodified (meth) aclylic resin, phenol modified (meth) aclylic resin, ormelamine modified (meth) aclylic resin may be used.

The acrylic resin emulsion, dispersion, or aqueous solution thatincludes a 1 to 99 wt % water-soluble acrylic resin is preferablyalkalescent; that is, it preferably has hydrogen-ion exponent in a rangeof pH7 to pH9. Such a water-soluble acrylic resin is well dispersed in asolvent such as water, and provides the paint film having advantageousfilm-forming and evenness, and high density and adhesion to a metaltarget substrate.

The acrylic resin preferably has a median diameter in a range of 50 to150 nm. The median diameter may be comparable to an average particlesize. Such an acrylic resin is well dispersed in a solvent such as waterand provides the paint film having advantageous film-forming andevenness, and high density and adhesion to a metal target substrate.More preferably, the acrylic resin has a median diameter in a range of60 to 140 nm, most preferably, 70 to 130 nm.

The polypropylene resin may be a homopolymer consisting of propylenemonomers, a random polymer that is a copolymer propylene including thepropylene and the ethylene with a small amount, or a block polymer thatis a homo-random copolymer including the propylene and the ethylenepropylene rubber (EPR). The polypropylene resin may be a modifiedpolypropylene resin or a chlorinated polypropylene resin.

The polypropylene resin emulsion, dispersion, or aqueous solution thatincludes a 1 to 99% polypropylene resin is preferably alkalescent; thatis, it preferably has hydrogen-ion exponent in a range of pH7 to pH9.Such a polypropylene resin is well dispersed in a solvent such as waterand provides the paint film having advantageous film-forming andevenness, and high density and adhesion to both metal target substratesand resin target substrates.

The polypropylene resin preferably has a median diameter in a range of50 to 150 nm. The median diameter may be comparable to an averageparticle size. Such a polypropylene resin is well dispersed in a solventsuch as water and provides the paint film having advantageousfilm-forming and evenness, and high density and adhesion to both metaltarget substrates and resin target substrates. More preferably, thepolypropylene resin has a median diameter in a range of 60 to 140 nm,most preferably, 70 to 130 nm.

The water-soluble resin content is determined by referring to thecharacteristics of target substrates or the use application of the paintfilm. Too small an amount of the water-soluble resin may fail to providethe paint film having intended adhesion to target substrates. Such apaint film may peel easily or the catalyst and the activated carbon mayeasily drop from the paint film. Too large an amount of thewater-soluble resin may fail to provide intended performance todecompose ozone. Thus, the water-soluble resin is present, for example,in a range of 5 to 100 parts by mass, preferably, 10 to 50 parts by massto per hundred parts by mass of total solid contents of the catalyst andthe activated carbon. Such a water-soluble resin content provides thepaint film having both high adhesion to target substrates and highperformance to decompose ozone.

In some embodiments, the water-based paint component may include apigment or an additive to have higher performance in accordance withpaint use application or paint purpose, for example, for rust preventionor for chipping resistance. Examples of the pigment include a colorpigment, an extender pigment, a rust preventive pigment, or a functionalpigment.

As the color pigment, for example, carbon black, titanium oxide, ironoxidize, zinc oxide, azo-type organic pigment, insoluble azo-typepigment, condensed azo, diketo-pyrrolo-pyrrole, benzimidazolon,phthalocyanine, indigo pigment, perinone, perylene, dioxane,quinacridone, isoindolinone, metal complex, chrome yellow, zinc ironoxide, red iron oxide, and titanium dioxide are employed.

As the rust preventive pigment, for example, zinc phosphate, zincphosphite, aluminium polyphosphate, aluminium tripolyphosphate, calciummolybdate, zinc orthophosphate, zinc polyphosphate, zinc molybdate, zincphosphomolybdate, aluminium phosphomolybdate, zinc oxide, zinc silicate,aluminium phosphate, calcium phosphate, zinc cyanamide, calciumcyanamide, barium metaborate, and magnesium phosphate are employed.

The rust preventive pigment that does not include toxic heavy metalsincluding the chromium is preferable from the viewpoint of environmentalprotection. The rust preventive pigment content is less than 30 mass %,preferably, less than 20 mass % in the paint film. Such a contentprovides the paint composition having good storage stability.

As the extender pigment, for example, the talc, calcium carbonate,barium sulfate, calcium sulfate, mica, kaolinite, silica, diatomite,alumina, baryta, and silicon dioxide are employed. In particular, thetalc has layer structures with high density in the paint film. Such atalc can prevent contamination of corrosion factors.

As the additive, for example, a viscosity modifier, film-forming aid,dispersant for dispersing the pigment, defoamer, filler, plasticizer,anti-sagging agent, coalesce, thixotropic agent, leveling agent, pHadjuster, neutralizer, ultraviolet absorbent, ultraviolet stabilizer,anti-settling agent, tackifier, curing catalyst, desiccant, stabilizer,and surface additive are employed.

As the dispersant for dispersing a pigment, a polycarboxylic acid-baseddispersant may be employed.

As the defoamer, a silicone-based or acrylic-based defoamer may beemployed. The defoamer prevents and destroys fine foam bubbles in mixingprocess and enables the paint composition to have intendedhomogenization and viscosity or fluidity. Additionally, the paintcomposition with few foam bubbles is less likely to cause rust resultingfrom moisture contamination from bubbles and thus has high performanceto prevent rust.

As the desiccant, for example, metal-based desiccants such as cobaltnaphthenate and lead naphthenate may be employed. The desiccantfacilitates dry in paint film-forming process and thus allows the paintfilm to have increased polymerization of the water-soluble resin andincreased density.

As the stabilizer, for example, alkanolamine derivatives such as thediisopropanolamine, ethanolamine, diethanolamine, diethanolamine,triisopropanolamine, triethanolamine may be employed. The stabilizerenables adjustment of fluidity, viscosity, or dispersion of the paintcontents and stabilization of the paint. The alkanolamine derivative mayaction as corrosion inhibitor for initial rust.

Thus, the water-based paint composition including the catalyst, theactivated carbon, the polyacrylate-based dispersion, the water-solubleresin, the pH adjuster and the water as a solvent are prepared throughthe dispersion step, the neutralization step, and the paint preparefinal step.

This water-based paint composition is applied to target substrates inknown painting way, for example, air spray, shower, spray, roll coater,flow coater, die coater, brush, immersion, drawing or ironing, knifecoater, bar coating, and electrostatic coating. The application amountand conditions are not limited. The target substrates are coated withthe paint having a predetermined thickness.

The water-based paint composition applied to target substrates isair-dried to evaporate or vaporize the solvent including water therein.Alternatively, it may be heat-dried at a predetermined temperature for apredetermined time or be force-dried using a dryer. Thus, the paintcomposition is dry-hardened. This drying yields a hardened paint film onthe target substrates. This hardened paint film from the water-basedpaint composition of the present embodiment includes the catalyst andthe activated carbon. Such a paint film has performance to decomposeozone.

In particular, the water-based paint composition of the presentembodiment includes the polyacrylate-based dispersion that enables thecatalyst and the activated carbon to be finely dispersed. Thispolyacrylate-based dispersion enables the catalyst and the activatedcarbon to have a maximum particle diameter (D_(max)) of, for example, 20μm or less, and cumulative 90% particle size (D90) of, for example, 10μm or less. The maximum particle diameter is determined by a linetransect method with a grind gauge on the basis of JISK 5600 and JISK5400. The cumulative 90% particle size (D90) or 90% diameter isdetermined by laser diffraction analysis with a laser diffractionparticle size analyzer.

Consequently, the paint film from the water-based paint composition, inwhich the catalyst and the activated carbon is finely and welldispersed, is less likely to have paint seeding and roughness. Such apaint film is excellent in film-forming and adhesion to targetsubstrates. Additionally, such a paint film has even surface and goodappearance. Thus, with thin film, for example, a dry film thickness ofjust 5 μm or less, the paint film can cover the target surfaces fully.Additionally, the paint film, which derives from the water-based paintcomposition that is applied to target surfaces and then is dried, can bemore strongly bonded to the target surfaces in comparison to the priorart in which a predetermined catalyst are stuck to a target substratesuch as a radiator using binders. In the prior art, the surface of asubstrate such as a radiator has binders to carry the predeterminedcatalyst. Thus, the surface of the substrate often catches foreignmatters such as dirt or dust. This causes reduction in the ozonedecomposition performance of the predetermined catalyst and activatedcarbon. The paint film from the water-based paint composition of thepresent embodiment is less likely to catch foreign matters such as dirtor dust and can prevent corrosion of a target substrate. Thus, thecatalyst and the activated carbon is prevented from degrading and lesspeelable from a target substrate after long use. Consequently, thecatalyst and the activated carbon keep high performance to decomposeozone for a longer time.

With the water-based paint composition according to the presentembodiment, the polyacrylate-based dispersion enables the particulatecatalyst and the particulate activated carbon to be well dispersed. Thisyields the fine particulate catalyst and the fine particulate activatedcarbon. Such a catalyst and an activated carbon adsorb a large amount ofozone. In particular, a small amount of the polyacrylate-baseddispersion achieves well dispersion of the catalyst and the activatedcarbon. Thus, the polyacrylate-based dispersion is unlikely to inhibitozone binding to the catalyst and the activated carbon. Adsorption of alarge amount of ozone is achieved with use of a small amount of thecatalyst and the activated carbon. Consequently, the water-based paintcomposition of the present embodiment has high performance to decomposeozone. Further, since the catalyst and the particulate are well andfinely dispersed using the polyacrylate-based dispersion, the paint filmis less likely to have paint seeding. Such a paint film is excellent inthin film-forming. Thus, the paint film from the water-based paintcomposition of the present embodiment exhibits excellent performance todecompose ozone even with a thin film.

Furthermore, the water-based paint composition including thepolyacrylate-based dispersion allows the catalyst and the activatedcarbon to be stably dispersed. The water-based paint composition is freefrom precipitate and separation resulting from agglomeration orflocculation, for example, for 1 month. The water-based paintcomposition has high storage stability.

When the water-based paint composition is applied to structures exposedto air-flow, such as car drive components such as a fan blade, aradiator, and a intercooler, and car exterior components such as anunder cover and a grille, a component coated with the paint film fromthe water-based paint composition reduces ozone around the componenteffectively. The ozone is decomposed on contact with the paint film.Thus, the ozone in air is removed.

Thus, the water-based paint composition is applied to car components, onwhich air flows when the car travels. The surfaces of the car componentsare coated with the paint film from the water-based paint composition.This paint film formed on the surfaces has performance to decomposeozone. In particular, the prepared water-based paint composition of thepresent embodiment includes the catalyst and the activated carbon thatare finely dispersed. This water-based paint composition can be appliedto car components and can be used over wide area of a car. Thus, the carcan be expected to have high performance to decompose ozone as a whole.

The examples of the water-based paint composition according to thepresent embodiment will be then described in detail.

The formulations of the examples of the water-based paint compositionaccording to the present embodiment is shown in TABLE 1.

TABLE 1 Com- Com- Com- Com- Com- Com- Formulations Example ExampleExample parative parative parative parative parative parative (in grams)1 2 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Dispersion Activated 3.6 3.6 3.6 3.6 3.6 3.6 3.6 3.6 3.6 step carbon(Solid content) Manganese 8 8 8 8 8 8 8 8 8 oxide-based catalystDispersant Poly- Poly- Poly- 0 Poly- Poly- Phosphate Poly- Poly-acrylate- acrylate- acrylate- carboxylic carboxylic ester urethanecarboxylic based based based acid acid acid ammonion sodium sodium saltsalt salt 0.5 0.5 1 0 1 1 1 1 3 Water 68.4 72.4 71.9 71.9 71.9 71.9 71.971.9 69.9 Neutralization Triethylamine 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 step (TEA) Paint prepare Acrylic resin 0 8 8 8 8 8 8 8 8 final stepPolypropylene 12 0 0 0 0 0 0 0 0 resin Additive 6 6 6 6 6 6 6 6 6 Total100 100 100 100 100 100 100 100 100 Storage stability Good Good Good NANA Poor Poor Poor Good Ozone decomposition Good Good Good NA NA FairFair Fair Poor Total evaluation Good Good Good Poor Poor Poor Poor PoorPoor

As shown in TABLE 1, the water-based painting composition according toExample 1 included an activated carbon, which is derived from coconutshell and has an average particle size of 5 μm and BET specific surfacearea of 2000 m²/g, a manganese oxide-based catalyst, which contains themanganese oxide of 70 wt % or more, and has an average particle size of5 μm and BET specific surface area of 250 m²/g, a polyacrylate-baseddispersant, water as a solvent, the triethylamine (TEA) as a pH adjusteror neutralizer, a polypropylene resin as a water-soluble resin, and anadditive such as a viscosity modifier or a thickener. In Example 2 andExample 3, the formulations were as in Example 1 except that thepolypropylene resin were replaced by an acrylic resin.

The activated carbon content shown in TABLE 1 is the solid activatedcarbon content. In TABLE 1, the water content in dispersion stepincludes a deionized water content as a solvent content and a watercontent that is included in the activated carbon product as a solventcontent.

To prepare the water-based painting composition according to Examples 1to 3, a dispersion step was firstly carried out. In the dispersion step,the activated carbon, the manganese oxide-based catalyst (hereinafter,referred to as “catalyst”), the water as a solvent, and thepolyacrylate-based dispersant were prepared and mixed according to theformulations shown in TABLE 1. The mixture is dispersed in a bead millfor 90 minutes at 1500 rpm. This bead mill was a zirconia bead millusing the zircon having 1.5 mm in diameter as media.

In Examples 1 to 3, this dispersion process yielded the activated carbonhaving a maximum particle diameter (D_(max)) of 20 μm or less andcumulative 90% particle size (D90) of 10 μm or less, and the catalysthaving a maximum particle diameter (D_(max)) of 20 μm or less andcumulative 90% particle size (D90) of 10 μm or less. The maximumparticle diameter was determined by a line transect method with a grindgauge on the basis of JISK 5600 and JISK 5400 (1990). The cumulative 90%particle size (D90) was determined by laser diffraction analysis with alaser diffraction particle size analyzer.

A neutralization step was then carried out. In the neutralization step,the dispersed mixture was neutralized by adding the triethylamine (TEA)as a pH adjuster to the dispersed mixture. This triethylamine (TEA) wasprepared according to the formulations shown in TABLE 1.

Subsequently, a paint prepare final step was carried out. In the paintprepare final step, the neutralized mixture was mixed with thepolypropylene resin having a solid content of 30 wt % as thewater-soluble resin or the acrylic resin having a solid content of 40 wt% as the water-soluble resin, and the additive such as a viscositymodifier or thickener. The resultant mixture was thoroughly stirredusing a disperser for 5 to 10 minutes.

In this way, the water-based painting composition according to Examples1 to 3 were prepared.

For comparison, some compositions of Comparative Examples 1 to 6 wereprepared according to the formulations shown in TABLE 1. ComparativeExamples 1 to 6 used some dispersants different from thepolyacrylate-based dispersant used in Examples 1 to 3 or did not use anydispersants.

Comparative Example 1 did not use any dispersants.

Comparative Example 2 used polycarboxylic acid ammonium salt (anion) asthe dispersant, instead of the polyacrylate-based dispersant used inExamples 1 to 3.

Comparative Examples 3 and 6 used polycarboxylic acid sodium salt(anion) as the dispersant, instead of the polyacrylate-based dispersantused in Examples 1 to 3.

Comparative Example 4 used phosphate ester as the dispersant, instead ofthe polyacrylate-based dispersant used in Examples 1 to 3.

Comparative Example 5 used polyurethane as the dispersant, instead ofthe polyacrylate-based dispersant used in Examples 1 to 3. ComparativeExamples 1 to 6 were prepared as in Examples 1 to 3.

Examples 1 to 3 and Comparative Examples 1 to 6, which were preparedaccording to the formulations shown in TABLE 1, were tested and assessedto storage stability and performance to decompose ozone.

In the test for storage stability, each prepared composition waspreserved for a month at 20° C. and whether each composition hasagglomeration or flocculation, or not was determined. The example thatdid not have agglomeration or flocculation even after preservation for 1month is determined to have good storage stability. The example that hadagglomeration or flocculation is determined to have poor storagestability.

The test for ozone decomposition was conducted using an ozonedecomposition testing device 100 shown in FIG. 1 . The testing device100 includes a pipe 10 in which a test specimen t was horizontallyplaced. This test specimen t was prepared by applying the paintcomposition to a polypropylene TP substrate 20 with 5 cm×7 cm indimensions and drying them at 100° C. for 10 minutes. The polypropyleneTP substrate 20 is termed “PP substrate 20” below. Thus, the testspecimen t included the PP substrate 20 that is covered with a hardenedpaint film 1 with 5 cm×7 cm in dimensions. This paint film covered overthe surface of the PP substrate 20.

Air including ozone was fed to the pipe 10 containing the test speciment so that the air flows through the pipe 10 at a speed of 10 meters persecond. It is note that the initial ozone concentration on the basis ofthe volume is 4.0 ppm at 25° C. While the air including ozone flowsthrough the pipe 10, the ozone concentration was measured using an ozonesensors 31 and 32. The concentration of the ozone before being passedthrough the test specimen t, which consists of the PP substrate 20covered with the paint film 1, was measured using the ozone sensor 31while the concentration of the ozone after passing through the testspecimen t was measured using the ozone sensor 32. Here, the distance xbetween the paint film 1 and the ozone sensor 32 was 2 mm. The ozoneconcentration was measured at room temperature 25° C. or near. Ozonedecomposition rate (%) of the paint film 1 was calculated using ozoneconcentration b1 measured by using the ozone sensor 31 and ozoneconcentration b2 measured by using the ozone sensor 32. Specifically,the ozone decomposition rate (%) is given by: (b1−b2)/b1×100. Theexample that provided ozone decomposition rate of 24% or more isdetermined to have good performance to decompose ozone. The example thatprovided ozone decomposition rate of 18% or more and less than 24% isdetermined to have fair performance to decompose ozone. The example thatprovided ozone decomposition rate of less than 18% is determined to havepoor performance to decompose ozone.

The example that has good storage stability and good performance todecompose ozone is determined to be good in a total evaluation. Otherexamples are determined to be poor in the total evaluation. The testresults are given in the lower column of TABLE 1.

With the water-based paint composition according to Examples 1 to 3, thepolyacrylate-based dispersant allowed the activated carbon and thecatalyst to be highly and stably dispersed. Thus, the water-based paintcomposition according to Examples 1 to 3 did not have agglomeration orflocculation after preservation for 1 month at 20° C. The water-basedpaint composition according to Examples 1 to 3 has good storagestability as shown in the lower column of TABLE 1.

With the water-based paint composition according to Examples 1 to 3, theparticulate activated carbon and the particulate catalyst were finelydispersed. Thus, the paint film from the water-based paint compositionaccording to Examples 1 to 3 had less paint seeding and roughness. Thepaint film having a dry film thickness of about 5 μm was sufficient tocover over the surface of a polypropylene substrate. Thus, the paintfilm from the water-based paint composition according to Examples 1 to 3is excellent in film-forming and ozone decomposition.

By contrast, the paint composition according to Comparative Example 1,which did not use any dispersants, had agglomeration or flocculation andgelation, which resulted from poor dispersion of the activated carbonand the catalyst. Thus, the paint composition according to ComparativeExample 1 did not have intended liquidity suitable for application.

The paint composition according to Comparative Example 2, which used thepolycarboxylic acid ammonium salt as a dispersant, also hadagglomeration or flocculation and gelation, which resulted from poordispersion of the activated carbon and the catalyst. Thus, the paintcomposition according to Comparative Example 2 also did not haveintended liquidity suitable for application.

The paint composition according to Comparative Example 3, which used thepolycarboxylic acid sodium salt (anion) as a dispersant, the paintcomposition according to Comparative Example 4, which used the phosphateester as a dispersant, and the paint composition according toComparative Example 5, which used the polyurethane as a dispersant, hadintended liquidity suitable for application. Unfortunately, ComparativeExamples 3 to 5 had poor dispersion and dispersion stability of theactivated carbon and the catalyst storage stability. Thus, ComparativeExamples 3 to 5 had agglomeration or flocculation after preservation for1 month at 20° C. Comparative Examples 3 to 5 has poor storagestability. Additionally, the activated carbon and the catalyst accordingto Comparative Examples 3 to 5 din not be finely dispersed, in contrastto Examples 1 to 3 using the polyacrylate-based dispersant. Thus,Comparative Examples 3 to 5 provided the paint film having a largeamount of paint seeding and large roughness. The paint film, which wasapplied to the surface of the substrate and covered over it, was verythick. Thus, Comparative Examples 3 to 5 exhibited poor film-forming.Comparative Examples 3 to 5 also exhibited inferior ozone decompositionrate as compared with Examples 1 to 3 using the polyacrylate-baseddispersant.

Comparative Example 6 exhibited improved storage stability because of ahigher dispersant content. Whereas, Comparative Example 6 exhibitedlower performance to decompose ozone. This may be because the highdispersant content causes the dispersant to inhibit ozone binding to thecatalyst and the activated carbon. The lower dispersant content fails toprovide intended storage stability. The higher dispersant content failsto provide intended performance to decompose ozone. This may be becausethe higher dispersant content causes the dispersant to inhibit ozonebinding to the catalyst and the activated carbon. Unlike Examples 1 to3, with the dispersants of Comparative Example 6, Comparative Example 6cannot have both good storage stability and performance to decomposeozone.

In Examples 1 to 3 using the polyacrylate-based dispersant, the catalystand the activated carbon is well and finely dispersed with the lowpolyacrylate-based dispersant content. Such a particulate catalyst andparticulate activated carbon is less likely to agglomerate orflocculate. Thus, Examples 1 to 3 is excellent dispersion and dispersionstability, and good storage stability. In addition, the paint film hadless paint seeding and roughness. Such a paint film has advantagefilm-coating and appearance. Thus, the paint film according to Examples1 to 3 exhibited high performance to decompose ozone.

In Examples 1 to 3, the polyacrylate-based dispersant, even with lowcontent, allowed the activated carbon and the catalyst to be finelydispersed. Such a finely dispersed activated carbon and catalyst adsorba large amount of ozone and provides high performance to decomposeozone. Thus, Examples 1 to 3 are excellent in ozone decomposition.Additionally, Examples 1 to 3 are excellent in dispersion stability andstorage stability, and has a long shelf life.

In Comparative Example 3 to 5, the activated carbon and the catalyst ispoor in dispersion. The paint composition according to ComparativeExample 3 to 5 has a large amount of agglomeration or flocculation.Thus, the paint film had a large amount of paint seeding and largeroughness. This paint film had poor film-forming, adhesion to thesubstrate, and appearance.

In Examples 1 to 3, the polyacrylate-based dispersant allows theactivated carbon and catalyst to be finely dispersed. Thus, the paintfilm was free of paint seeding and roughness. This paint film had goodfilm-forming and appearance. Additionally, Examples 1 to 3 used thepolypropylene resin or the acrylic resin as the water-soluble resin.Thus, Examples 1 to 3 exhibited high adhesion to metal substrates.Specifically, with the paint film according to Examples 1 to 3, thenumber of squares peeled off from a metal substrate was two or less inadhesion test described in detail below. In particular, the Examples 2and 3, which used the polypropylene resin as the water-soluble resin,exhibited high adhesion to not only the metal substrate but also a resinsubstrate. In the adhesion test of Examples 2 and 3, the number ofsquares peeled off from the resin substrate was two or less. Thus, useof the polypropylene resin as the water-soluble resin achieves highadhesion to both the metal substrate and the resin substrate. Thecomposition using the polypropylene resin as the water-soluble resindoes not require a special device for improvement of adhesion. Thus,such a composition can be provided at low cost. Use of the acrylic resinas the water-soluble resin achieves high adhesion to the metalsubstrate. When the composition using the acrylic resin as thewater-soluble resin is applied to resin substrate, it is preferable thatthe composition is applied to preprocessed resin substrate for allowingthe paint film to be strongly bond to the substrate.

The inventors determined a preferred polyacrylate-based dispersantcontent in detail as shown in TABLE 2.

In TABLE 2, the prepared paint compositions were different in thepolyacrylate-based dispersant content (in grams). These prepared paintcompositions were the same content except for the polyacrylate-baseddispersant as Example 2 shown in TABLE 1.

The paint compositions of TABLE 2 used the same materials as the paintcompositions of TABLE 1. The paint compositions of TABLE 2 were preparedas described above, TABLE 1.

The paint compositions of TABLE 2, which were different in thepolyacrylate-based dispersant content, were also tested and assessed inthe same manner as described above, as in TABLE 1, for storage stabilityand ozone decomposition rate (referring to FIG. 1 ).

TABLE 2 Polyacrylate-  0.1  0.3  0.5  0.7  1.0  2.0  5.0 10.0 baseddispersant content (gram) Concentration  0.1  0.3  0.5  0.7  1.0  2.0 4.8  9.1 of polyacrylate- based dispersant in water-based paintcomposition (mass %) Polyacrylate-  0.9  2.6  4.3  6.0  8.6 17.2 43.186.2 based dispersant content (parts by weight) per hundred parts byweight of total amount of activated carbon and manganese oxide-basedcatalyst Storage stability Poor Good Good Good Good Good Good Good Ozone24.9 25.6 24.8 24.7 25.1 25.3 18.4 10.2 decomposition rate (%)

The paint composition that included 0.1 mass % polyacrylate-baseddispersant, or 0.9 parts by mass of the polyacrylate-based dispersantper hundred parts by mass of the total solid content of the activatedcarbon and the catalyst had poor dispersion stability of the activatedcarbon and the catalyst as shown in TABLE 2. This composition hadagglomeration or flocculation after preservation for 1 month at 20° C.The paint composition that included 9.1 mass % polyacrylate-baseddispersant, or 86.2 parts by mass of the polyacrylate-based dispersantper hundred parts by mass of the total solid content of the activatedcarbon and the catalyst exhibited low ozone composition rate. This maybe because the large dispersant content causes the dispersant to inhibitozone binding to the catalyst and the activated carbon.

The paint composition that included 0.3 to 4.8 mass % polyacrylate-baseddispersant, or 2.6 to 43.1 parts by mass of the polyacrylate-baseddispersant per hundred parts by mass of the total solid content of theactivated carbon and the catalyst had good dispersion and dispersionstability of the activated carbon and the catalyst. Additionally, thiscomposition, in which the dispersant did not inhibit ozone binding,exhibited high ozone composition rate. Thus, this composition withoptimal polyacrylate-based dispersant content exhibited both gooddispersion stability and good performance to decompose ozone.

Further, the content of the polyacrylate-based dispersant not less than1.5, more preferably, not less than 2, most preferably, not less than2.5 by mass, per hundred parts by mass of the total solid content of theactivated carbon and the catalyst, provides excellent storage stability.The content of the polyacrylate-based dispersant not more than 75, morepreferably, not more than 60, most preferably, not more than 50 by mass,per hundred parts by mass of the total solid content of the activatedcarbon and the catalyst, provides the paint film having goodfilm-forming and appearance, and high performance to decompose ozone.

Thus, it is preferable that the polyacrylate-based dispersant content isin a range of 1.5 to 75 by mass, per hundred parts by mass of the totalsolid content of the activated carbon and the catalyst. Such a contentprovides both excellent storage stability and high performance todecompose ozone. Additionally, this content provides good film-forming,adhesion and appearance of the paint film. It is more preferable thatthe polyacrylate-based dispersant content is in range of 2 to 60 bymass, most preferably, 2.5 to 50 by mass, per hundred parts by mass ofthe total solid content of the activated carbon and the catalyst.

It is preferable that the polyacrylate-based dispersant is present inthe water-based paint composition at a concentration in a range of 0.3to 5 mass %. This concentration provides both excellent storagestability and high performance to decompose ozone. Additionally, thisconcentration provides good film-forming, adhesion and appearance of thepaint film. It is more preferable that the polyacrylate-based dispersantis present in the water-based paint composition at a concentration in arange of 0.3 to 2 mass %.

The inventors also determined a preferred activated carbon content and apreferred catalyst content in detail as shown in TABLE 3 and TABLE 4below.

The paint compositions of TABLE 3, which were different in the ratio ofthe activated carbon to the catalyst, were prepared to determine therelation between the ratio of the activated carbon to the catalyst, andthe properties of the paint compositions and the performance of thepaint film from the paint compositions. The paint compositions of TABLE3 used the same materials as the paint compositions of TABLE 1. Thepaint compositions of TABLE 3 were prepared as described above, TABLE 1.The prepared paint compositions of TABLE 3 were also tested for storagestability and ozone decomposition rate.

The storage stability test was conducted in the same manner as describedabove, as in TABLE 1. That is, the presence or absence of agglomerationor flocculation in the prepared paint compositions after preservationfor 1 month at 20° C. was determined. The paint composition that had asmall amount of agglomeration or flocculation after preservation for 1month but had liquidity suitable for application or practical usethrough agitation is determined to have fair storage stability.

The ozone decomposition test was conducted as shown in FIG. 2 .Specifically, a test specimen t was prepared by applying the paintcomposition to a polypropylene TP substrate 20 with 5 cm width×7 cm longand drying them at 100° C. for 10 minutes. This paint compositioncovered over the surface of the substrate 20. The test specimen t wasplaced in a 20 litre volume mylar bag 50. Air was put into the bag 50 byusing an air blow device, and ozone generated by using an ozonizer wasthen put into the bag 50 such that the bag 50 contains 0.2 ppm ozone (onthe volumetric basis). The bag 50 was then heat-sealed. After 30minutes, ozone concentration in the bag 50 was measured by using anozone sensor 33. Ozone decomposition rate is calculated in accordancewith initial ozone concentration and after 30 minutes ozoneconcentration measured by using an ozone sensor 33. The ozonedecomposition test was conducted at room temperature 25° C.

For comparison, Comparative Examples 7 and 8 were prepared. ComparativeExamples 7 and 8 used only one of the activated carbon or the catalyst.Comparative Examples 7 and 8 were also tested for storage stability andozone decomposition rate.

The formulations of the prepared paint compositions are given in uppercolumns of TABLE 3 and the test results are given in lower columns ofTABLE 3.

The activated carbon content shown in TABLE 3 is the solid activatedcarbon content. In TABLE 3, the water content in dispersion stepincludes a deionized water content as a solvent content and a watercontent that is included in the activated carbon product as a solventcontent.

TABLE 3 Formulations Example Example Example Example Example ComparativeComparative (in grams) 4 5 6 7 8 Example 7 Example 8 Activatedcarbon/manganese 20/80 30/70 50/50 70/30 80/20 0/100 100/0 oxide-basedcatalyst (ratio) Dispersion Activated carbon 2.3 3.5 5.8 8.1 9.3 0 11.6step (Solid content) Manganese oxide- 9.3 8.1 5.8 3.5 2.3 11.6 0 basedcatalyst Polyacrylate-based 0.5 0.5 0.5 0.5 0.5 0.5 0.5 dispersant Water68.4 68.4 68.4 68.4 68.4 68.4 68.4 Neutralization Triethylamine 1.5 1.51.5 1.5 1.5 1.5 1.5 step (TEA) Paint prepare Polypropylene 12 12 12 1212 12 12 final step resin Additive 6 6 6 6 6 6 6 Total 100 100 100 100100 100 100 Storage stability Good Good Good Good Fair Good Poor Ozonedecomposition rate (%) 80.0 83.0 83.1 81.9 76.0 75.9 50.0

As shown in TABLE 3, Comparative Example 7, which used the catalyst butnot used the activated carbon, exhibited an ozone decomposition rate of75.9%, which is lower than that that of Examples 4 to 8. ComparativeExample 8, which used the activated carbon but not used the catalyst,exhibited an ozone decomposition rate of 50.9%, which is much lower thanthat of Examples 4 to 8. Comparative Example 8 exhibited poor or badstorage stability. This is because that the particulate activated carbonhaving an adsorption property adsorbed a large amount of resin ororganic matter in the paint composition and thus agglomerated orflocculated. It has been found that only use of the catalyst providespoor paint stability, specifically poor storage stability.

Examples 4 to 8 using both the activated carbon and the catalystprovided much higher ozone decomposition rate than Comparative Examples7 and 8 using only one of the activated carbon or the catalyst. Examples4 to 8 exhibited very high performance to decompose ozone.

Thus, both the catalyst and the activated carbon are required todecompose ozone efficiently. However, it is noted that the higherproportion of the activated carbon to the catalyst may adversely affectthe stability, specifically storage stability of the paint composition.Further, the activated carbon is susceptible to oxidation anddeterioration. Thus, the higher proportion of the activated carbon tothe catalyst may fail to provide long life performance to decomposeozone. It is also note that the lower proportion of the activated carbonto the catalyst may fail to provide the intended performance todecompose ozone and intended synergistic effects of the activated carbonand the catalyst. This is because the lower the proportion of theactivated carbon to the catalyst is, the smaller the effect of ozonedecomposition of the activated carbon is. In particular, the catalyst issusceptible to moisture, chloride, sulfur oxides (SO_(x)), and nitrogenoxides (NO_(x)) in atmosphere. These matters may decrease ozonedecomposition performance of the catalyst. Thus, it is preferable that apredetermined amount of the activated carbon is used to retain highperformance to decompose ozone over long.

Specifically, it is preferable that the ratio of the activated carbon(solid content) to the catalyst in the water-based paint composition isin a range of 20/80 to 80/20 to provide high performance to decomposeozone and practical storage stability as Examples 4 to 8 shown in TABLE3. In particular, it is more preferable that the ratio of the activatedcarbon to the catalyst in the water-based paint composition is in arange of 30/70 to 70/30 to provide higher performance to decompose ozonefor long term and excellent storage stability for long term as Examples5 to 7. It is noted that the ratio of the activated carbon to thecatalyst in the water-based paint composition equates with the ratio ofthe activated carbon to the catalyst in the paint film from thewater-based paint composition. When the ratio of the activated carbon tothe catalyst in the water-based paint composition is in a range of 20/80to 80/20, the ratio of the activated carbon to the catalyst in the paintfilm from the water-based paint composition is also in a range of 20/80to 80/20.

Further, the paint compositions that are different in the totalconcentration of the activated carbon and the catalyst were prepared asshown in TABLE 4 to determine the relation between the paint filmperformance and the concentration of the activated carbon and thecatalyst, which have performance to decompose ozone. The paintcompositions and the paint films from the paint compositions of TABLE 4have the same ratio (by weight) of the activated carbon (solid content)to the catalyst, 70/30, as in Example 7 of TABLE 3. The paintcompositions and the paint films of TABLE 4 are different in theactivated carbon content and the catalyst content. In the paintcompositions and the paint films of TABLE 4, the activated carbon andthe catalyst are present at a concentration in a range of 33 to 83% bymass. The formulation except for the activated carbon and the catalystof the paint compositions of TABLE 4 were the same as that of Example 7.The paint compositions of TABLE 4 were prepared as described above,TABLE 3. In TABLE 4, the component content (in grams) except for theactivated carbon content and the catalyst content were as in Example 7.TABLE 4 differs from Example 7 in the activated carbon content and thecatalyst content.

The prepared paint compositions of TABLE 4 were tested for ozonedecomposition rate and adhesion to a substrate.

The ozone decomposition test was conducted by using the device shown inFIG. 1 as in TABLE 1 and TABLE 12 described above.

In the adhesion test, a test specimen was prepared by air-spraying thepaint composition on a polypropylene substrate and by drying them at100° C. for 10 minutes. Thus, the test specimen was formed of thepolypropylene substrate coated with the paint film. This test specimenwas tested with respect to adhesion in compliance withJIS-K-5600-5-6:1999 (cross-cut test). Specifically, the coated surfaceof the test specimen was cross-cut to make 11 slits at 1 mm intervalsrespectively by using a utility knife. This cross-cut formed 100squares, each of which is 1 mm×1 mm. An adhesive tape (masking tape) wasthen put on the 100 squares followed by putting pressure on the tape.Subsequently, the tape on the 100 squares was peel off in one sitting,and the number of the peeled squares was counted. The paint film inwhich the number of the peeled squares was two or less is determined tohave good adhesion. The paint film in which the number of the peeledsquares was three or more is determined to have poor adhesion.

The total concentrations of the activated carbon and the catalyst in theprepared paint compositions are shown in upper columns of TABLE 4 whilethe test results are shown in lower columns of TABLE 4.

TABLE 4 Total concentration of activated carbon and manganeseoxide-based catalyst in paint-film contents (mass %) 33% 53% 63% 73% 83%Activated carbon/ 70/30 manganese oxide-based catalyst Ozonedecomposition rate (%) 1.23 5.80 19.61 25.25 25.61 Adhesion Good GoodGood Good Fair

It was found that the higher concentration of the activated carbon andthe catalyst equates with the higher ozone decomposition rate as shownin TABLE 4. In particular, the paint film that includes the activatedcarbon and the catalyst at concentration of 63% or more exhibited higherozone decomposition rate. It is noted that the paint films that includethe activated carbon and the catalyst at concentration of 73% or moreexhibited the small increase rate of the ozone decomposition rate. Thismay be because dispersion of a predetermined amount of the dispersantmay be limited.

Too high a concentration of the activated carbon and the catalyst mayadversely affect adhesion. Low adhesion to the substrate may cause thepeeling of the paint film or the falling of the paint film contents.Thus, the long life performance to decompose ozone may not be obtained.

It has been found that the paint film including the activated carbon andthe catalyst that are present at a concentration of 60% or more,preferably, 70% or more provides high performance to decompose ozonewhen the ratio of the activated carbon (solid content) to the catalystin the paint composition and the paint film is in the range of 20/80 to80/20. Additionally, it has been found that the paint film including theactivated carbon and the catalyst that are present at a concentration of90% or less, preferably, 85% or less provides high adhesion to thesubstrate. The activated carbon and the catalyst are preferably presentin the paint film at a concentration in a range of 60% to 90%, morepreferably, 70% to 80%. Such a content provides high adhesion to thesubstrate and high performance to decompose ozone for a long term.

The total concentration (in wt %) of the activated carbon and thecatalyst in the paint film from the paint composition is calculated bydividing the total solid amount of the activated carbon and the catalystby the total solid paint content in the paint composition, andmultiplying the resultant by 100.

As described above, the water-based paint composition according to theembodiment includes a water-based solvent, a manganese dioxide-basedcatalyst as a manganese dioxide-based catalyst, an activated carbon, apolyacrylate-based dispersant, an acrylic resin or a polypropylene resinas a water-soluble resin, the triethylamine as a pH adjuster. Thewater-based paint composition is applied to substrates and then dried.This yields a hardened paint film.

The process for preparing the water-based paint composition according tothe embodiment includes a dispersion step of mixing and dispersing wateras a principal component of a solvent, a manganese dioxide-basedcatalyst as a manganese dioxide-based catalyst, an activated carbon, apolyacrylate-based dispersant, a neutralization step of mixingtriethylamine as a pH adjuster with the resultant mixture, and a paintprepare final step of mixing and dispersing an acrylic resin or apolypropylene resin as a water-soluble resin with the resultant mixture.

With the water-based paint composition according to the embodiment ofthe present invention and the process for preparing the water-basedpaint composition according to the embodiment of the present invention,the polyacrylate-based dispersant provides good and stable dispersion ofthe manganese dioxide-based catalyst and the activated carbon. Thisprovides the hardened paint film with paint seeding free. Such a paintfilm has good film-forming and good adhesion. The fine dispersedmanganese dioxide-based catalyst and the fine dispersed activated carbonin the paint film adsorb a large amount of ozone. Thus, the paint filmhas high performance to decompose ozone. In particular, the manganesedioxide-based catalyst, which has higher catalytic activity for ozonedecomposition among manganese oxide-based catalysts, provide higherperformance to decompose ozone. Further, the combination use of themanganese dioxide-based catalyst and the activated carbon provideshigher performance to decompose ozone than if only one or the other isused. Additionally, the paint composition using the activated carbon,which is available at low cost, is less expensive. Furthermore, thepaint composition including the polyacrylate-based dispersant, whichallows the manganese dioxide-based catalyst and the activated carbon tobe highly dispersed, has good storage stability for practical use.

The manganese dioxide-based catalyst preferably has a median diameter ina range of 1 to 20 μm and a specific surface area in a range of 100 to400 m²/g determined by the BET method. The median diameter may becomparable to an average particle size. Such a manganese dioxide-basedcatalyst exhibits stable dispersion. This provides the paint compositionhaving higher dispersion and dispersion stability and the paint filmhaving higher performance to decompose ozone.

The activated carbon preferably has a median diameter in a range of 1 to20 μm and a specific surface area in a range of 500 to 3000 m²/gdetermined by the BET method. The median diameter may be comparable toan average particle size. Such an activated carbon exhibits stabledispersion. This provides the composition having higher dispersion anddispersion stability and the paint film having higher performance todecompose ozone.

The polyacrylate-based dispersant preferably has a weight averagemolecular in a range of 5000 to 30000, an acid value in a range of 1 to50, and a hydrogen-ion exponent in a range of pH4 to pH9. Such apolyacrylate-based dispersant, even with a small amount, achieves higherdispersion and dispersion stability of the paint contents, as well ashigh performance to decompose ozone. The polyacrylate-based dispersantis preferably present at 1.5 to 75 parts by mass, per hundred parts byweight of the total solid amount of the manganese oxide-based catalystand the activated carbon. Such a content provides the water-based paintcomposition having both high storage stability and high performance todecompose ozone. The polyacrylate-based dispersant is preferably presentin the water-based paint composition at a concentration in a range of0.3 to 5 mass %. Such a concentration provides the water-based paintcomposition having both high storage stability and high performance todecompose ozone.

In the water-based paint composition of above embodiments, the manganeseoxide-based catalyst and the activated carbon have a maximum particlediameter (D_(max)) of 20 μm or less. The maximum particle diameter isdetermined by a line transect method with a grind gauge according to JISK 5600 and JIS K 5400 (1990). The manganese oxide-based catalyst and theactivated carbon are dispersed using a bead mill or a roll mill, andhave a maximum particle diameter of 20 μm or less through a dispersionstep.

This provides paint film with agglomeration or flocculation free, higherforming-film and adhesion. Additionally, such a manganese oxide-basedcatalyst and an activated carbon adsorb a larger amount of ozone, thusproviding higher performance to decompose ozone. Further, such amanganese oxide-based catalyst and an activated carbon provides thewater-based paint composition having excellent dispersion stability andstorage stability.

Thus, the water-based paint composition has long shelf life and thepaint film from the water-based paint composition has stable paintperformance.

In the water-based paint composition of above embodiments, the manganeseoxide-based catalyst and the activated carbon have a 90% diameter (D90)of 10 μm or less. The 90% diameter (cumulative %) is based on a volumedistribution and is determined by laser diffraction analysis. Themanganese oxide-based catalyst and the activated carbon are dispersedusing a bead mill or a roll mill, and have 90% diameters (D90) of 10 μmor less through a dispersion step.

The water-based paint composition including the manganese oxide-basedcatalyst and the activated carbon that have a 90% diameters (D₉₀) of 10μm or less has a small amount of coarser grains such as agglomerationand flocculation. Thus, this water-based paint composition provides thepaint film having less paint seeding and evenness. Such a paint film isexcellent in forming-film and adhesion. Additionally, the paint filmhaving less agglomeration and flocculation adsorbs a large amount ofozone and have high performance to decompose ozone. Further, thiswater-based paint composition is excellent in dispersion stability andstorage stability.

Thus, the water-based paint composition has higher storage stability andthe paint film from the paint composition is excellent in visualappearance and high performance to decompose ozone.

In the water-based paint composition of above embodiments, thewater-based resin is an acrylic resin or a polypropylene resin. Theacrylic resin and the polypropylene resin are compatible with themanganese oxide-based catalyst and the activated carbon. Thus, themanganese oxide-based catalyst and the activated carbon is moreuniformly dispersed in the resin. In particular, the acrylic resin has awide variety of a molecular weight. Thus, the use of the acrylic resinmay easily yield the paint film having desired performance.Additionally, the acrylic resin provides the paint film having highweather resistance, water resistance, and chemical resistance. Thepolypropylene resin provides the paint film having good adhesion toresin substrates in addition to metal substrates. Such a paint film haslong-term high performance to decompose ozone.

The solid weight ratio of the manganese oxide-based catalyst to theactivated carbon is preferably in a range of 20/80 to 80/20, morepreferably, 30/70 to 70/30 in the water-based paint composition. Such aratio allows the manganese oxide-based catalyst and the activated carbonto act synergistically, thus providing higher performance to decomposeozone, as well as good storage stability.

The manganese oxide-based catalyst and the activated carbon ispreferably is present in the paint film from the water-based paintcomposition at total concentration in a range of 60 to 90%, morepreferably, 65 to 85%, most preferably, 70 to 80% by mass. This provideshigher performance to decompose ozone, as well as high adhesion tosubstrates.

In some embodiments, the activated carbon may carry organometalliccomplexes, for example, including cobalt or iron. The manganeseoxide-based catalyst may include calcium oxide adsorbing moisture.

The water-based paint composition according to the present embodimentcan be used in car bodies. Further, the water-based paint compositionmay be used in trains, ships, airplanes, or buildings. Furthermore, thewater-based paint composition may be used in office automation equipmentor electrical equipment including dry copiers, ozonizers, ultravioletray lamps, and air purifiers for dedorization, sterization, and breach.For example, the water-based paint composition may be used in thehousing of purifying devices, the casing, exhaust filter, exhaust duct,or exhaust fan of ozone generators with high voltage or corona dischargefor decomposing residual ozone.

The present invention is not limited to above mentioned embodiment withrespect to other formulations, contents, components, amounts, particlesize of the water-based paint composition. In addition, not all of thenumeric values described in the present embodiment indicate a criticalvalue, and a certain numeric value indicates a preferred value for theembodiment. A little variation is acceptable.

The invention claimed is:
 1. A water-based paint composition,comprising: a manganese oxide-based catalyst; an activated carbon; apolyacrylate-based dispersant; a water-soluble resin; a pH adjuster; anda water-based solvent.
 2. The composition according to claim 1, whereinthe manganese oxide-based catalyst is a manganese dioxide-basedcatalyst.
 3. The composition according to claim 1 or 2, wherein themanganese oxide-based catalyst and the activated carbon are present in aratio having a range of 20:80 to 80:20.
 4. The composition according toclaim 1, wherein the manganese oxide-based catalyst and the activatedcarbon are present in a range of 60 to 90% by mass in total to totalsolid contents.
 5. The composition according to claim 1, wherein thepolyacrylate-based dispersant has a weight average molecular weight in arange of 5000 to 30000, acid value in a range of 1 to 50, andhydrogen-ion exponent (pH) in a range of 4 to
 9. 6. The compositionaccording to claim 1, wherein the polyacrylate-based dispersant ispresent in a range of 1.5 to 75 parts by mass per hundred parts by totalweight of the manganese oxide-based catalyst and the activated carbon.7. The composition according to claim 1, wherein the manganeseoxide-based catalyst has a maximum particle diameter (Dmax) of 20 μm orless determined by grind gauge, and the activated carbon has a maximumparticle diameter (Dmax) of 20 μm or less determined by the grind gauge.8. The composition according to claim 1, wherein the manganeseoxide-based catalyst has a 90% diameter (D90) of 10 μm or lessdetermined by laser diffraction analysis, and the activated carbon has a90% diameter (D90) of 10 μm or less determined by the laser diffractionanalysis.
 9. The composition according to claim 1, wherein thewater-soluble resin is an acrylic resin or a polypropylene resin.